In the patent to Ostrom, U.S. Pat. No. 3,778,180 there is shown a specially designed drill bit for use in drilling holes in printed circuit boards wherein the spirally arranged grooves extend from the bit into the shank to facilitate rejection of the drilled material, shavings and the like which tend to cling to the shoulders. In the patent to Shaner, U.S. Pat. No. 3,667,857, there is disclosed a drill bit provided with conventional helical grooves and between these grooves additional helical grooves of lesser depth provided with notched leading edges which supplement those of the conventional grooves. The discontinuity of the teeth are alleged to facilitate chip removal, reduce resistance to rotation of the tool, provide for closer tolerances and to provide for operation at relatively lower speeds and temperatures thereby increasing the tool life and eliminating the necessity of reaming operations.
The drill bit of this invention is designed especially for drilling printed circuit boards to eliminate the problems heretofore encountered and specifically to provide burr free, smear free and stress free holes within allowable tolerances as to size, without need for cleaning processes and to improve the life and cutting characteristics of the drill. This is achieved herein by providing the conventional twist drill with auxiliary cutting edges which function primarily to remove the material generated by the cutting edges of the spiral grooves, the formation of which reduces the surface area of the drill bit in contact with the hole being generated thereby reducing the friction and enabling maintaining drill speed without overheating which is the primary cause of smearing and pitting and which places limitations on the speed of operation.